如何用按键控制RecyclerView滚动？滚动失效问题求助

Hey there! Let's break down your two RecyclerView key-scrolling questions clearly, and fix that frustrating issue you're facing.

There are a few reliable ways to get your RecyclerView scrolling with key presses:

• Basic Key Listener Setup: Attach an OnKeyListener to your RecyclerView to listen for directional keys (up/down/left/right), then trigger scroll actions manually. You can use methods like recyclerView.smoothScrollBy(dx, dy) for smooth scrolling, or layoutManager.scrollToPosition(targetPosition) to jump directly to a specific item.
• Leverage LayoutManager Methods: Most LayoutManagers (including FlexboxLayoutManager) have built-in scroll methods. For example, layoutManager.scrollToPositionWithOffset(position, offset) lets you scroll to an item and position it at a specific offset from the top/bottom of the RecyclerView.
• Focus-Based Automatic Scrolling: If your RecyclerView items are focusable (set android:focusable="true" in item layouts), RecyclerView will automatically scroll to bring focused items into view when you press directional keys. This is the most seamless approach if focus management works for your use case.

From your description, the problem is that your focused yellow ImageView (outside the RecyclerView) isn't triggering the scroll to the green ImageView inside the RecyclerView. Here's why that's happening and how to fix it:

Root Cause #

The key press events are being consumed by the focused yellow ImageView, not passed to the RecyclerView. Even if they were, the RecyclerView isn't focused, so it won't respond to scroll commands by default.

Solutions #

Option 1: Redirect Key Events from the Yellow ImageView to RecyclerView

Add a key listener to your yellow ImageView to capture the down key press, then transfer focus to the RecyclerView and trigger the scroll to your target position:

// Get reference to your yellow ImageView
ImageView yellowImageView = findViewById(R.id.your_yellow_imageview_id);

yellowImageView.setOnKeyListener((view, keyCode, event) -> {
    // Only handle key down events for the down directional pad key
    if (event.getAction() == KeyEvent.ACTION_DOWN && keyCode == KeyEvent.KEYCODE_DPAD_DOWN) {
        // Request focus for the RecyclerView so it can respond to scroll actions
        recyclerView.requestFocus();
        
        // Replace `targetPosition` with the actual position of your green ImageView in the adapter
        int targetPosition = 3; 
        // Use smooth scroll for a nicer user experience, or scrollToPosition for instant jump
        recyclerView.smoothScrollToPosition(targetPosition);
        
        return true; // Mark the event as handled
    }
    return false; // Let other events propagate normally
});

Option 2: Ensure RecyclerView Can Receive Focus

Make sure your RecyclerView is set up to accept focus, either via XML or code:

// In code
recyclerView.setFocusable(true);
recyclerView.setFocusableInTouchMode(true);

// Or in your layout XML
<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recyclerView"
    ...
    android:focusable="true"
    android:focusableInTouchMode="true"/>

Option 3: Use Focusable Items for Automatic Scrolling

If your green ImageView is part of a RecyclerView item, set that item (or the ImageView itself) to be focusable. Once the item has focus, pressing the down key will automatically scroll the RecyclerView to bring the next focused item into view:

<!-- In your RecyclerView item layout -->
<ImageView
    android:id="@+id/greenImageView"
    ...
    android:focusable="true"
    android:focusableInTouchMode="true"/>

Quick Check for FlexboxLayoutManager #

Ensure you're using the latest version of the FlexboxLayoutManager library to avoid any known scrolling/focus bugs. Also, double-check that your layout manager's flex settings aren't causing items to be laid out in a way that blocks scroll detection.

内容的提问来源于stack exchange，提问作者typebreaker